Disused lamps are most conveniently disposed of by crushing into pieces of a size small enough for industrial or commercial refuse collection. Manual disposal inevitably means smashing lamps with an iron bar or throwing bricks at them such that razor sharp glass splinters tend to fly in every direction and a worker's eyes are particularly vulnerable if not protected. Moreover with some lamps there is a serious danger of injury from fire or hazardous chemicals.
Sodium vapour lamps contain metallic sodium which, when released burns fiercely in contact with water--even moisture in the air. Indeed, when a skip full of such lamps is manually smashed and doused the sodium/water reaction is very fierce and the flames may harm an unwary worker. Also the old manual method of smashing lamps in a skip and then hosing can leave some lamps unbroken or just cracked. These could break at any time and start a fire in the skip, refuse truck or rubbish heap. Moreover, in metallic sodium and the caustic soda which is formed when it reacts with water will both burn skin and eyes, on contact therewith, so careless disposal can lead to injury. Furthermore, since hydrogen gas, which creates an explosive atmosphere when mixed with air at 4% concentration, is formed when sodium reacts with water, haphazard manual disposal in inadequately ventilated skips or refuse containers could lead to a dangerous build up of this explosive gas.
Mercury vapour lamps, of course, contain mercury which is a poison since it vaporises at room temperature and is thus absorbed into the body. It must be disposed of carefully and not allowed to escape to water systems and pollute the environment. Fluorescent tubes contain small amounts of other poisons such as strontium, cadmium and lead which may be breathed in during manual lamp disposal.
Manual disposal also tends to mean that large quantities of used lamps are stacked up in odd heaps in depots or vehicles for days or weeks before disposal. Because they must be stored in dry areas, this wastes space. The risk of fire in the storage area is also a problem where sodium lamps are concerned. If just one sodium vapour lamp is cracked the sodium may react with moisture in the air and cause a serious fire, and/or give rise to the other dangers mentioned above. Similarly there is a risk of pollution where disused mercury lamps or fluorescent lamps are stored for long periods of time.
To obviate the above-discussed health and fire risks it is necessary to crush disused lamps in a closed, suitably vented container and spray water onto the contents to quench any sodium/water reaction.